The RBI imposed the fines over the past four days, according to stock exchange filings by the banks, though specifics of the non-compliance were not disclosed.

The Reserve Bank of India (RBI) has fined at least 19 lenders, including top banks such as ICICI Bank and State Bank of India, for failing to comply with its guidelines on the use of global payments network SWIFT.

The RBI imposed the fines over the past four days, according to stock exchange filings by the banks, though specifics of the non-compliance were not disclosed.

Four bankers whose institutions were fined said that most of the issues related either to interpretation of the RBI's guidelines or minor technical matters.

"These are petty, procedural issues like counterparty confirmation and nothing major or structural," said one banker who is directly aware of the matter but declined to be named because he is not authorised to speak to the media.

The penalties totalled more than 400 million rupees ($5.67 million) and ranged from 10 million rupees to 40 million rupees for each bank, the filings showed.

The Indian banking system was sent reeling early last year by a $2 billion fraud at state lender Punjab National Bank (PNB), resulting from unauthorised credit guarantees to businesses linked to billionaire jeweller Nirav Modi and his uncle Mehul Choksi via SWIFT.

"The series of fines imposed is a stern signal from RBI to banks to strengthen their internal systems and minimise fraud after the PNB fraud last year, which tarnished the image of India's banking system," said Mitul Budhbhatti, associate director and head of banking, financial services and insurance at CARE Ratings.

"I expect RBI to continue to be more and more vigilant and continue with such monitoring."

After the PNB loan fraud, which prompted criticism of the RBI by the government for its lack of regulatory oversight, the central bank had sent a confidential directive to banks about how they must use the SWIFT payment system, requiring most banks to overhaul their financial systems.

Most notable among those rules was the requirement for banks to connect the SWIFT interbank messaging system with their core banking software by April 30 last year.

However, gaps in compliance were found in more than two dozen places, prompting the RBI to impose the fines.

The RBI had conducted the audits at banks 8-10 months ago and issued show-cause notices four months ago. Since the notices were issued, banks have plugged those holes, bankers said.

"After the show-cause notices were issued to us, we have addressed those minor points," said one banker.